When an internal combustion engine is shut off, unburned hydrocarbon fuel vapors may be left in an intake manifold system, engine cylinders and/or an engine crankcase. These hydrocarbon fuel vapors may migrate out of the engine cylinders through an open intake valve into the intake manifold along with vapors that have migrated from a crankcase to the intake manifold through a PCV (Positive Crankcase Ventilation) system. The vapors in the intake manifold may also migrate past the throttle and into the fresh air intake system and then out into the surrounding atmosphere. Further, vapors may also migrate from a crankcase, through a crankcase fresh air hose, to the fresh air intake system and then out into the surrounding atmosphere. The migration of the hydrocarbon fuel vapors has been shown to be enhanced by the rising and falling temperatures of the engine during engine off soak which can be caused by rising and falling ambient temperatures or other like conditions.
It is known in the art to add an air induction system (AIS) hydrocarbon (HC) trap comprising one or more hydrocarbon adsorbing surfaces within the AIS to adsorb vaporized hydrocarbons during engine off soaks to prevent or reduce the release of such hydrocarbons into the environment. These AIS hydrocarbon traps may be purged of the temporarily adsorbed hydrocarbon vapors when the engine is restarted and the vapors may be consumed during normal engine combustion.
In one approach disclosed in U.S. Patent application 2003/0192512, a hydrocarbon trap is shown as a metal structure which may be coated with an appropriate adsorber and comprised of cells or rings. In another approach disclosed in U.S. Pat. No. 6,905,536 a second AIS hydrocarbon trap may include rings pleated with angled or radiused folds, forming concentric or acentric cylinders within cylinders, with intermediate, inner and outer support members interceding between the rings. The ring material may adhere to itself along a mating edge to form a ring, and may further adhere to support members. In both approaches, one or more adsorbing surfaces may run parallel to the direction of an air flow axis, to define one or more adsorbing channels, disposed in a housing and/or coupled to a flange for installation.
The inventors herein have recognized various issues with such approaches. In some examples, the adsorbing channels defined in AIS hydrocarbon traps, such as the above described, may require different dimensions for different applications. For example, in some engines, the engine volume may be greater than in other engines, requiring a larger mass of air per engine cycle and larger adsorber channel openings. The prior AIS hydrocarbon traps are difficult to scale and without scalable adsorbing channel openings, the trap may impede an engine's ability to take in air and may result in engine efficiency being degraded. Further still, due to the construction and organization of a vehicle, there may be space limitations and size and material constraints on the AIS hydrocarbon trap. Increasing the density of cells or changing the pleat or ring dimension may not address the needs of a particular engine configuration or operating condition as current AIS hydrocarbon traps may not be easily altered to the requirements and dimensions of different systems.
As discussed above, the current AIS hydrocarbon traps may not be readily scalable or translatable across different applications and use in different operating conditions. For example, increasing a number of concentric or acentric cylinders within cylinders in an AIS hydrocarbon trap may increase the weight supported by pleats and intermediate members, leading to structural instability. Further, structural instability may change adsorber channel opening area, adsorbing surface, and adsorbing surface area in an undesired manner.
Further, current AIS hydrocarbon traps may couple the housing and the adsorbing material of the trap together using fasteners, screws, moldings, and/or adhesives. However, such fasteners and/or adhesives may breakdown over time resulting in the trap degrading and needing to be replaced. As an example, wear and tear due to vehicle operation may lead to degradation and deformation of the fasteners and/or adhesives and may cause a loss of functionality of the trap. When functionality is lost, AIS hydrocarbon traps may not meet full lifetime durability requirements and may need to be replaced. Further, loss of functionality may also lead to safety related issues due to parts of AIS hydrocarbon traps being ingested into the engine.
Accordingly, devices and methods are disclosed for an improved AIS hydrocarbon trap. In one example, the disclosed AIS hydrocarbon trap includes a trap housing enclosing an adsorber roll, where the adsorber roll includes a hydrocarbon adsorbing material, and a corrugate support rolled together. In some examples, the improved AIS hydrocarbon trap may be formed by rolling the corrugate support and adsorbing material into a wound adsorber roll and installing the roll in the trap housing. As such, in some examples, the AIS hydrocarbon trap may be spiral-shaped. The improved AIS hydrocarbon trap may have improved scalability, simplified construction, improved durability and a high level of adaptability for use in a variety of systems.
The disclosed AIS hydrocarbon trap may be a lightweight construction which may be easily adaptable and scalable. The AIS hydrocarbon trap's scalability allows optimization of cross sectional area, so that normal engine intake operations may not be inhibited while maintaining hydrocarbon trap effectiveness. Adsorber channel opening size and adsorbing surface area may be easily controlled with the AIS hydrocarbon trap construction such that it can be adapted to specific engine air flow and vaporized hydrocarbon adsorption requirements. For example, adsorbing material length and width may be controlled to enable a desired mass of air per engine cycle to move through adsorbing channels to the engine and for the AIS hydrocarbon trap to be employed in applications requiring differing adsorption surface area.
It should be understood that the background and summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.